1. Field of the Invention
The present invention relates to a system and method for testing an individual's sensitivity to light.
2. Description of the Prior Art
Several devices and methods have been proposed for measuring a subject's sensitivity to glare or light possessing significant intensity and prescribing tinted lenses as a result. Generally, the subject views a test pattern through an aperture or port while the intensity of a light source is increased to inhibit the visual acuity of the test subject viewing the test pattern. The subject indicates at which point the test pattern is no longer clear or visible or at which point the subject begins to experience visual discomfort and a reading is taken. Differently tinted lenses may then be inserted between the eyes of the test subject and the light source to determine if any improvement in visual acuity results. The test patterns used are generally letters, symbols, or other patterns developed in the ophthalmic industry for the special purpose of testing a subject's perception of contrasting objects.
One such effort is described in U.S. Pat. No. 3,425,772 to Minas wherein the inventor provides a device for measuring retinal irradiation or the point when the periphery of a light source appears to increase. The device itself includes a light source arrangement comprising two elongated light sources or a circle and point source configuration which are illuminated to form light peripheries. The respective light is intensified and the peripheries merge to appear as a single light source upon which event the test subject notifies the test supervisor. The irradiation point is equated to a chart generated by running a series of examinations on individuals to establish a range. A tinted lens is then prescribed to the patient to increase the intensity at which retinal irradiation occurs.
In U.S. Pat. No. 2,209,978 to Higley, the inventor produced another device of this nature called a glaremeter for determining sensitivity to glare for instance, when viewing the oncoming lights of an automobile. The glaremeter includes a housing with an aperture on one end for viewing into a compartment. Situated within the compartment is a light and reflector for focusing the rays of light onto the eyes of the observer. The observer views a series of letters appearing at the opposite end of the compartment while a second light source is gradually illuminated until the objects are visible to the observer which is announced to the test supervisor. Rotatable disks upon which are mounted differently tinted lenses are positioned within the compartment in line with one of the light sources and a light meter reading is taken. Differing colored lenses are rotated between the light source and light meter to reduce the light meter's reading and determined the proper lens prescription.
Other devices of this nature can also be found in U.S. Pat. Nos. 5,007,730 to McAllister; 4,800,404 to Ginsburg et al.; 4,764,007 to Task; and 3,684,355 to Molner. In general, the test subject views a test pattern such as letters or other symbols through an aperture or viewing port of a box while a glare source is increased to obscure the viewer's vision at which point the viewer indicates that the target is no longer clear or visible. Lenses may then be used to reduce the glare effects.
Yet another attempt at this type of device is the Sunglass Doctor.TM., distributed by Brain Power, Inc., which is understood to be intended to reveal which sunglass lens best protects a patient's eyes. A device is provided to produce a test pattern as the test subject focuses on this pattern while holding a release button. A light source is gradually increased and the patient releases the button when the test pattern is no longer visible. The release of the button triggers a meter to provide a percentage density as an indication of the recommended solar prescription.
A common theme carried throughout the above-mentioned efforts is that they are all missing the ability to simulate realistic situations in which sunlight is encountered. Instead, these devices merely provide a test pattern or target consisting of alphanumeric characters or symbols established within the ophthalmic industry to have well known features for providing varying degrees of contrast and requiring varying degrees of visual acuity to perceive them. A variable intensity light source is then introduced to obscure the observer's visual acuity. Thus, the introduced glare emanates from a single source instead of multiple sources that occur in outdoor settings.
However, the settings in which sunglasses are used are typically outdoors during recreational activities with a wide range of stimulus presenting itself to the sunglass wearer. In other words, blinding glare often arises from a variety of sources and not merely a single point light source such as a headlight. Additionally, the above-references devices are also primarily focused on prescribing different tinted lenses as opposed to determining the optimum color of a lens under a variety of reflective and glare conditions.
What is still needed therefore, is a testing apparatus that conveniently presents realistic images and facilitates the determination of the proper color and tint of sunglass lenses to maximally reduce discomfort of the test subject under all sorts of outdoor lighting conditions.